U.S. application Ser. No. 07/772,216, now, U.S. Pat. No. 5,176,961, filed Oct. 7, 1991 by us under the title COLORED, TEXTURED GLASS-CERAMIC ARTICLES and assigned to the assignee of the present application, now U.S. Pat. No. 5,176,961 observes that, whereas colored glazes certainly add beauty and variation to ceramic articles, there is an inherent sameness in appearance in glaze-coated articles, which sameness is exaggerated in articles having broad surface areas such as large sheets for architectural applications. The premise underlying the disclosure of U.S. Pat. No. 5,176,961 resided in the belief that an improvement in the surface character of a glaze would add another dimension to the aesthetic appearance of glaze-coated articles. Accordingly, the primary objective was to develop a process for producing glass-ceramic articles exhibiting a variegated color, surface textured appearance.
That objective was accomplished through a process involving five general steps:
(a) a batch for a glass having a base composition capable of being converted through heat treatment to a glass-ceramic article and containing a colorant is melted;
(b) that melt is cooled and a colored glass frit prepared therefrom;
(c) a batch for a glass having a base composition essentially the same as the base composition of the glass of Step (a) and, optionally, containing a colorant is melted;
(d) that melt is formed into a desired shape while in the molten state;
(e) particles of colored glass frit are dispersed atop the surface of the molten glass shape;
(f) the molten glass shape is cooled to a solid glass article; and then
(g) the solid glass article is heat treated to cause the solid glass article and the colored glass frit particles to crystallize in situ thereby forming a glass-ceramic article having a variegated colored, textured surface.
Such articles exhibit a very striking appearance, combining a wide variety of colors and topical surface effects. However, as can be appreciated from the above outline of the process, the number of steps involved and the high degree of care demanded in carrying out the steps to assure uniformity of product appearance [particularly Step (e)] result in a relatively expensive final product.
Therefore, the underlying objective of the present invention was to devise another method for decorating ceramic articles through the application of glazes which could impart a surface textured appearance, where desired, but which could be more readily controlled to yield products of uniform appearance.
A specific objective was to devise such a method for decorating glass-ceramic architectural cladding members and tableware.